I do not drive a BA but some straight forward mods you could do would be to switch to lighter seats
. Move the battery to the boot and switch it to an Optima
unit Not just weight savings but improved balance there. I saw a carbon fibre boot advertised from the same people who do the bonnets.
More difficult but ultimately more telling would be to switch to an alloy block. Perhaps a modified brake system using the DBA 5000 series
lightweight two piece discs and some Wilwood Billet Dynalite
calipers? Always nice to reduce unsprung weight. Might also be some advantage to be had switching to a coilover setup although costly for a decent threaded type.